White LEDs (“WLEDs”) have gained significant importance in the applications of general illumination market and display market. One example is the WLED street lamp application. Currently LED backlight power supplies typically use a three-stage driver system. Some other power supplies are also required for the LED backlight driver system, for example, 12V, and/or 5V.
There are several kinds of structures for LED backlight driver system, some examples are shown in FIG. 1A, FIG. 1B and FIG. 2. A power structure 100A for a three-stage LED backlight driver system with two isolated voltage converters is shown in FIG. 1A. Power structure 100A comprises a power factor correction (“PFC”) stage, two isolated DC/DC (direct current to direct current) voltage converter stages, and a non-isolated LED driver stage. The PFC stage rectifies an AC (alternating current) voltage, e.g., 220V or 110V, to a DC (direct current) line voltage, e.g., 400V or 200V. One of the isolated DC/DC voltage converters is used to provide a DC power supply, e.g., 12V or 5V. And the other isolated DC/DC voltage converter is used to provide power for the LED driver stage. A power structure 100B for another three-stage LED backlight driver system with two isolated voltage converters is shown in FIG. 1B. Similar with power structure 100A, power structure 100B comprises a PFC stage, two isolated DC/DC voltage converter stages, and a non-isolated LED driver stage. One of the isolated DC/DC voltage converters is used to provide a DC power supply, such as 5V. And the other isolated DC/DC voltage converter is used to provide power for the LED driver stage and other DC power supply, such as 12V. FIG. 2 illustrates a power structure 200 for a three-stage LED backlight driver system with one isolated voltage converter. Power structure 200 comprises a PFC stage, an isolated DC/DC voltage converter stage, and non-isolated converters stage. The non-isolated converters comprise a LED driver and two non-isolated DC/DC converters. The isolated DC/DC voltage converter is used to provide power for the LED driver and the two non-isolated DC/DC converters.
The conventional LED backlight driver system comprises multiple converters such as isolated converters, non-isolated converters, and LED driver stage. The conventional LED backlight driver system is complex, has low efficiency and high costs.